1. Field of the Invention
This invention relates, in general, to a dual spark-plug ignition internal combustion engine in which two spark plugs are disposed in each combustion chamber to ignite the air-fuel mixture mixed with a portion of the exhaust gases provided into the combustion chamber, and, more particularly, to the configuration of the wall surface of the combustion chamber of the same engine.
2. Description of the Prior Art
In order to suppress the generation of nitrogen oxide (NOx) during combustion of the air-fuel mixture in the combustion chambers of automotive internal combustion engines, it has already been proposed that two spark plugs are disposed spaced apart in the combustion chamber to ignite and combust an air-fuel mixture mixed with a considerably large proportion of the exhaust gases fed into the combustion chamber. In general, as the amount of the exhaust gas feed increases, the combustion time is prolonged and accordingly the engine running becomes unstable. However, by the effect of the above-mentioned two spark plug ignition, the combustion time of the mixture in the combustion chamber is shortened, causing stable and smooth running of the engine.
Furthermore, the thus arranged engine is required improve and stabilize the combustion in the combustion chamber in order to achieve further decrease of the emission level of NOx without deterioration of stable engine running.